That being the case, I would be more than happy to make the new sprites needed for the 8 new skills. If you can send me over the frame-by-frame sprites as they are currently, that would be very handy as a guide for what's needed.
If you have NeoLemmix V12.0.0 or higher (ideally, V12.6.0 or higher, as these include a couple of new sprites for the Shimmier skill), then look in styles\default\lemmings and styles\xmas\lemmings for the standard and xmas sprites respectively. The "scheme.nxmi" file is a text-based file, and describes the recoloring for certain states as well as the hotspot and frame counts for each graphic. (Note that these frame counts are purely for visuals; the physics frame count for actions where this matters is hardcoded and cannot be changed short of hacking the EXE or a source code modification.)
If you haven't already, you might want to try out the new skills in-game too, either by playing content that contains it (Lemmings Plus VI is a good one that's not too hard, although it doesn't use the Shimmier skill - the Shimmier is a very recent addition and wasn't in NL yet when LPVI came out, and was only included in a stable release about a month ago; I don't really think there is much content that
does use it yet). It might be easier to think about how such sprites should look after seeing them in action.
The Disarmer currently has a graphic nearly identical to the Digger. We need a unique sprite for it even at low-res, but no one has made one yet.
As for the Xmas sprites, I'm pretty sure these already exist in WinLemm style (they feature in both Lemmini and SuperLemmini, so someone must have them somewhere, or maybe they're extractable from the Lemmini directories?)
They definitely don't exist officially. If SuperLemmini has them, Tsyu may have created them himself, or found them as part of some Lemmini fan-created content. They also could be direct upscales of the low-res sprites, or direct recolors of the non-xmas sprites.
Just so I'm clear as to what you mean by "graphics sets", are you referring to the individual components that make up a level such as terrain, objects, liquid, etc?
Ah, "graphic set" is a bit of an outdated term now, we usually call them "styles", but old habits die hard. Anyway, a graphic set or a style refers to the
collection of components - objects, terrain, backgrounds, lemming sprites, etc; some styles might not have all of these elements. In the case of the official DOS Lemmings games, we have 10 graphic sets - from Orig, "Dirt", "Fire", "Marble", "Pillar" and "Crystal"; from OhNo, "Brick", "Rock", "Snow" and "Bubble", and then the Xmas style from Holiday Lemmings. (One thing to note here is that Xmas mostly has the same terrain pieces as Snow; and as such, NeoLemmix has merged the terrain pieces from it into the Snow style; so NL's Xmas style only has objects and lemming sprites.)